Polymerisation of ethylene or propylene with heterogeneous metallocene catalysts on clay minerals

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Heterogeneous metallocene catalysts avoid reactor fouling in olefin polymerisations. For technical use the metallocene catalysts must be fixed on carriers. Silica is one of the favoured inorganic carriers. But the activities of heterogeneous metallocene catalysts on silica in ethylene and propylene polymerisation are often lower than those of comparable homogeneous catalyst systems. We tested the clay minerals kaolin and montmorillonite as inorganic carriers for the polymerisation of ethylene and propylene with commercially available titanocenes and zirconocenes and also with new types of titanocenes. The heterogeneous catalysts on kaolin were less active in ethylene polymerisation as comparable homogeneous catalysts and they were not active in propylene polymerisation. In contrast the heterogeneous catalysts on montmorillonite are often more active in ethylene or propylene polymerisation than comparable homogeneous systems. As cocatalysts trimethylaluminium (AlMe 3, TMA) and triisobutylaluminium (Al( i Bu 3), TIBA) were used for heterogeneous polymerisations. As catalysts commercially available titanocenes and zirconocenes and also four titanocenes with unusual structures were tested which Lang et al. had synthesised. The high activities in ethylene or propylene polymerisations with montmorillonite may be due to the special structure of the montmorillonite carrier.